Including letters of recommendation with freshman applications to Berkeley positively affected the enrollment of underrepresented students, according to a new study from the California Policy Lab.

UC Berkeley commissioned the study of its pilot recommendation-letters program to determine how the letters had an impact on diversity in campus admissions.

Study author Jesse Rothstein is co-director of the California Policy Lab and a UC Berkeley professor of economics and of public policy who has conducted academic research on admissions at UC and elsewhere. He called the letters an important addition to UC’s existing holistic admissions review processes.

Among Rothstein’s key findings, he said, is that the letters raised reviewers’ scores more — by as much as four percentage points — for applicants from underrepresented groups than for others, and the impact was concentrated among those with moderate likelihoods of admission for whom a small boost might have been quite important. Members of underrepresented groups are defined as those from families with low incomes, those whose parents did not attend college, those from low-performing schools and underrepresented racial and ethnic minorities.

Unlike most other highly selective universities, UC Berkeley has traditionally not asked for letters of recommendation from teachers or mentors as part its application process. With the number of applicants seeking admission to UC Berkeley growing each year, in 2015 and 2016 the university invited about 30 percent of freshman applicants to submit letters of recommendation, with the intent of learning more about them.

Rothstein said he plans to examine the performance of students admitted to UC Berkeley under the letters-of-recommendation pilot program, and to test if particular profiles of students or of letters are associated with greater effects on admissions decisions or on the quality of those decisions.